MySQL: Alternatives to ORDER BY RAND()

Question

I've read about a few alternatives to MySQL's ORDER BY RAND() function, but most of the alternatives apply only to where on a single random result is needed.

Does anyone have any idea how to optimize a query that returns multiple random results, such as this:

   SELECT u.id, 
          p.photo 
     FROM users u, profiles p 
    WHERE p.memberid = u.id 
      AND p.photo != '' 
      AND (u.ownership=1 OR u.stamp=1) 
 ORDER BY RAND() 
    LIMIT 18 

Answer 1

Order by rand() is very slow on large tables,

I found the following workaround in a php script:

Select min(id) as min, max(id) as max from table;

Then do random in php

$rand = rand($min, $max);

Then

'Select * from table where id>'.$rand.' limit 1';

Seems to be quite fast....